Integrated circuits can contain several million transistors on a single integrated circuit substrate. In order to interconnect these transistors to form a working device, as many as ten or more layers of conductive material may be formed overlying the substrate and the transistors to functionally interconnect the transistors. This interconnection or coupling is accomplished by the use of contacts or via structures.
Vias are typically openings etched through dielectric layers between the conductive layers. In modern semiconductor chip technology, vias are physically very small, the area of a via being limited to the area defined by the conjunction of signal wiring shapes on the corresponding layers. For example, due to the fine lithographic features that can be manufactured, many vias have dimensions of less than one micron. For example, 0.1 micron wide wires can have a via of 0.1 micron wide by 0.1 micron wide. In practice, the via might even be smaller to allow for misregistration of the via on the wires, or to allow for other process tolerances. However, the extremely small size of the vias increases the probability, given normal process defect densities and tolerances, of defects and hence degraded device performance and yield.
As electronic circuit densities increase and technology advances, for example, in deep sub-micron circuits, there is a need to maximize the utilization of the design layout and manufacturability and reliability of the circuit. This can be accomplished, for example, by adding redundant vias and the like. Thus, some design systems or graphics technicians will, after normal wiring is complete, add redundant vias, where possible, to enhance yield. However, these added vias, in many instances, can be located very close to one another or near edges of the wires, resulting in or increasing the probability of via to adjacent via or wire shorting. Also, it is known that densely packed vias suffer from processing problems such as over etching of the underlying dielectric layer, to name but one problem.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.